Snow particles produced from carbon dioxide are used in a wide variety of cooling and freezing applications. Carbon dioxide snow particles may be used, for instance, in refrigeration, for process cooling and freezing, as well as in the production of dry ice. More particularly, such snow particles are useful in both food and non-food applications, such as for example, in food cooling, freezing and refrigeration, and for rapid and/or spot cooling during the processing of various non-food materials.
Carbon dioxide snow particles are typically produced by rapid expansion of liquid carbon dioxide through a small orifice. The liquid carbon dioxide is obtained by compressing carbon dioxide gas and maintaining it under proper pressure and temperature conditions for refrigeration. In bulk storage tanks, for example, carbon dioxide stored at a pressure of approximately 300 lbs. per square inch and a temperature of about 0.degree. F. is in the form of a liquid. At the point of use, the liquid carbon dioxide is converted to a mixture of carbon dioxide snow and vapor by rapid expansion through a small orifice.
Prior art apparatuses for the production of carbon dioxide snow-making employ relatively simple orifices to enable an expansion to occur of the carbon dioxide liquid feed. However, typically, prior art expansion device/nozzles such as snow horns and orifices, create a spot impingement pattern, and are bulky and difficult to fit into small spaces. These prior art device/nozzles are also known to thrust the snow particles out of the snow horns and orifices at a high velocity. The high velocity of the carbon dioxide snow creates difficulty in applying an even snow blanket and can damage fragile items, such as cheese toppings on pizza or whipped toppings on bakery items. Furthermore, when used in process cooling applications, the high velocity can cause pitting on the surface, or even breakage, of fragile materials such as coated barrier materials. Moreover, the high velocity output of snow particles creates high noise levels that arise safety and environmental concerns with respect to personnel working in the vicinity.
Attempts have been tried to overcome the uneven application of carbon dioxide snow. For instance, specially shaped horns have been provided at the exit of an expansion orifice; fixed orifices have been used which discharge against a bounce plate; variable orifices have been used which discharge into closed containers and combinations of the above have all been attempted.
For instance, U. S. Pat. No. 3,667,242 to Kilburn describes a structure for producing carbon dioxide snow where liquid carbon dioxide is directed into an upper portion of a hollow, double-side-walled cylindrical horn which is provided with an open bottom and a closed top. A nozzle in the upper-most portion of the cylindrical horn imparts a swirling tangential movement to the snow formed in the horn.
U.S. Pat. No. 4,111,362 to Carter, Jr. describes a carbon dioxide snow making nozzle arrangement wherein pairs of carbon dioxide jets are transversely arranged so as to inject carbon dioxide into a horn region. The expanding jet mixtures of snow and vapor are directed into collision paths and thereby dissipate the energy of the jets.
U.S. Pat. No. 4,145,894 to Frank et al. describes a carbon dioxide snow production apparatus wherein liquid carbon dioxide is directed into a chamber through a nozzle. The resultant snow is dispersed by a motor driven drum with brush-like blades which pick up the snow and deposit it onto articles being moved along a conveyor belt.
U.S. Pat. No. 4,376,511 to Franklin, Jr. describes a carbon dioxide snow forming device wherein a manifold is positioned within a channel member and carbon dioxide snow is dispensed towards the sides of the channel member, thereby causing some of the kinetic energy of the carbon dioxide snow to be dissipated.
U.S. Pat. No. 4,462,423 to Franklin, Jr. describes a carbon dioxide snow-forming header wherein plural nozzles are positioned along a header pipe to enable plural dispensing regions for carbon dioxide snow along the header.
U.S. Pat. No. 4,640,460 to Franklin, Jr., describes a carbon dioxide snow-forming header wherein a pair of nozzles are provided within a tank. A supply of liquid carbon dioxide at approximately 300 psi is fed to the inlet ends of the nozzles. In addition, liquid carbon dioxide is applied to the inlet ends of the nozzle through a supply line so as to chill the supply line to an extent sufficient to reduce the temperature of the liquid carbon dioxide being supplied to the triple-point.
U.S. Pat. No. 5,020,330 to Rhoades et al., describes a food freezer which includes one or more nozzles for directing carbon snow particles onto food products. The liquid carbon dioxide is piped so that it flows only upwardly and/or horizontally toward the spray nozzles. Thus, any solid carbon dioxide that may accumulate adjacent the upstream side of the orifices is melted by carbon dioxide vapor which gravitates upward in the piping.
There is a need for carbon dioxide snow dispensing heads and nozzles which produce a fine particulate snow, wherein high velocity snow particles are avoided. Further, such devices should produce carbon dioxide snow particles of relatively constant particle dimensions so as to assure a relatively even application of the particles across food or other products or materials being cooled.
Accordingly, it is an object of this invention to provide an improved nozzle structure for production of fine carbon dioxide snow particles.
It is another object of this invention to provide an improved structure for providing finely divided carbon dioxide snow particles wherein nozzle blockage by solidified carbon dioxide particles is avoided.